GENERAL VIEWS. 
185 
middle limestone in Coverdale ; that under the Simonside limestone in 
Coverdale ; that under the Hardrow limestone at Gale and Aysgill. 
The gritstones contain rarely traces of terrestrial plants : where of a 
cherty nature, or unusually calcareous (as in Penyghent) marine exuvite 
become proportionably numerous. Organic remains are more numerous 
and varied in the lower limestone than in the Yoredale series. It is from 
this rock that the numerous fossils of Belgium, Mendip, South Wales, 
North Wales, Ireland, Derbyshire, and South Yorkshire are collected. 
Polyparia, crinoidea, conchifera, brachiopoda, gasteropoda, cephalopoda, 
Crustacea, — all are most plentiful in the lower rock. But its great su- 
periority in this respect vanishes away in those directions where the 
interpolations of gritstone and plate become frequent— as for example 
in Aldstone moor, and generally in Northumberland and Scotland. In 
the Yoredale series, the greatest abundance of fossils is found in or close 
to beds of limestone. Particular beds of limestone are marked (locally) 
by the prevalence of certain fossils : the Cam limestones (No. 4 and 5) 
are usually composed of little else besides fragmentary stems and plates 
of the bodies of crinoidea, producing the remarkable crinoidal marble 
of Garsdale, like some analogous but older beds in Derbyshire, Bolland, 
and Greenhow hill : lithodendra abound (locally) on the top of the 
Hardrow scar lime both in Coverdale, under Penyghent, in Wensleydale, 
Swaledale, and Aldstone moor: producta gigantea abounds in most 
localities in the upper dark layers of the lower limestone, alternating 
with shale, (Hawes) also in the Hardrow scar limestone, (Askrigg) and 
in the main limestone (Rokeby). The shells of cephalopodous mollusca 
are very rarely found among the rocks of the Yoredale series except in 
the shales below the Cam limestones. Here orthocerata, ammonites 
sphericus, a. striatus, bellerophon Woodwardii, naut. sulcatus, occur. 
The organic remains are not at all worn ; but retain all their sharp 
processes, spines, &c. in perfection, except in particular situations 
^as in the conglomerate limestone which lies on the grauwacke near 
Ingleton, and Horton.) 
These circumstances are perhaps not sufficient to justify the conclu- 
b b 
